Add envelopes (#30298)

* Add envelopes

* oops

* Remove unused loc string

* comments and fixes

Content.Client/Paper/EnvelopeSystem.cs

@@ -0,0 +1,35 @@
+using Content.Shared.Paper;
+using Robust.Client.GameObjects;
+
+namespace Content.Client.Paper;
+
+public sealed class EnvelopeSystem : VisualizerSystem<EnvelopeComponent>
+{
+    public override void Initialize()
+    {
+        base.Initialize();
+        SubscribeLocalEvent<EnvelopeComponent, AfterAutoHandleStateEvent>(OnAfterAutoHandleState);
+    }
+
+    private void OnAfterAutoHandleState(Entity<EnvelopeComponent> ent, ref AfterAutoHandleStateEvent args)
+    {
+        UpdateAppearance(ent);
+    }
+
+    private void UpdateAppearance(Entity<EnvelopeComponent> ent, SpriteComponent? sprite = null)
+    {
+        if (!Resolve(ent.Owner, ref sprite))
+            return;
+
+        sprite.LayerSetVisible(EnvelopeVisualLayers.Open, ent.Comp.State == EnvelopeComponent.EnvelopeState.Open);
+        sprite.LayerSetVisible(EnvelopeVisualLayers.Sealed, ent.Comp.State == EnvelopeComponent.EnvelopeState.Sealed);
+        sprite.LayerSetVisible(EnvelopeVisualLayers.Torn, ent.Comp.State == EnvelopeComponent.EnvelopeState.Torn);
+    }
+
+    public enum EnvelopeVisualLayers : byte
+    {
+        Open,
+        Sealed,
+        Torn
+    }
+}